If the current line comes underground via ducting then the fibre will likely take the same route.
The fact you have been able to make an FTTP order with BT means OpenReach already have the fibre Distribution Point (known as a CBT) in place at your nearest telegraph pole or underground chamber.
At this point you don't need to do anything except pick where you would like your ONT to go.
OpenReach will come out and survey the property to decide how they are getting the fibre from the CBT to your property.
You shouldn't need to do anything.
If you enter your address in to the BT Broadband Availability Checker sometimes it tells you the method they will use, sometimes not.
Enter your address here:
https://www.broadbandchecker.btwholesale.com/#/ADSL
Look for the part that says
Our records show the following FTTP network service information for these premises:
If your property has already been surveyed the next sentence may tell you what they are going to do.
Edit: dect beat me to it. Follow their advice.
Edited by j0hn83 (Fri 16-Jul-21 17:35:55)